SAMPLING METHODS

Remember:

How do we pick our sample? • 6 main kinds of sampling• The kind of sampling you choose depends on the type of

survey you are conducting

Simple Random Sampling• Each member of the population has an equal chance of

being selected• E.g., to select a random sample of 5 students from this

class, each student is assigned a number and 5 numbers are drawn from a hat

Systematic or interval sampling• Every nth member of the population is selected• E.g., in a factory, perhaps every 20th product in an

assembly line is tested for quality

Cluster Sampling• Every member of each randomly chosen group of the

population is selected• E.g., each grade represents a group of the school

population. One grade at GVC is chosen randomly and all students in that grade are selected.

Self-selected sampling• Only members who are interested will participate• E.g., if a radio station conducts a phone survey, only

people who are interested will call

Convenience Sampling• Only members of the population who are convenient to

include are selected• E.g., for a survey about grocery buying habits, people in a

grocery store are approached and questioned

Stratified Random Sampling• Some members from each group of the population are

randomly selected• E.g., 5 randomly chosen people from 3 different racial

groups

Group activity• Move into table groups (5 people/table)• 1 scenario/table - solve

Follow-up activity – 2-3 people1. Identify a potential problem with each sampling methoda) Suppose you want to know whether most people enjoy shopping. You survey the shoppers at a local mall. b) The cook in the school cafeteria surveys the teachers to find out which items to sell.

2. Explain whether each sample is appropriate.c) A TV show asks viewers to text their opinions about the decreased speed limit in town.d) To determine if customers are pleased with the service in a restaurant, every 8 th customer is polled on a given

day.

3. In each case, will the selected sample represent the population? Explain. e) To find out if the arena should offer more public skating times, a survey is posted on a bulletin board in the arena

and left for patrons to complete.f) To find out the favourite breakfast food of Grade 9 students, a survey of 300 randomly-chosen Grade 9 students

was conducted.

4. To determine citizens’ view of new parking fines, the mayor invites listeners to call in during a radio show. Do you think the results will accurately reflect the opinions of all citizens? Explain.

5. A survey reports: 50 Canadians say that the most important issue Canadians face is global warming. g) Do you think this sample is representative of the population? Explain.h) How might this sample have been selected. i) Suppose you were to repeat the survey. How would you select a sample? Explain how your choice of sample

would represent the population.

/9 marksDUE TOMORROW